Transformer

ABSTRACT

A transformer made of a multilayer construction in which plural spiral primary-side coils of thin plate and plural spiral secondary-side coils of thin plate are layered in turn. The primary-side coils of the multilayer construction are connected each other, the secondary-side coils of the multilayer construction are connected each other, an upper shielding layer of thin plate is disposed on the uppermost layer of the multilayer construction, and a lower shielding layer is disposed under the lowermost layer of the multilayer construction.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to a transformer used for variouselectronic appliances.

[0003] 2. Description of the Related Art

[0004] A transformer is, for example, used for an AC adaptor. Generally,a portable electronic appliance, including a secondary battery, gainsnecessary direct current from a commercial power source through the ACadaptor as an outside power supplier to charge the secondary battery anddrive the main body.

[0005] Generally, an AC adaptor provided with a transformer may havevarious box-type configurations of which size varies according torequired electric power, and switching regulator method is exclusivelyused to compose the electric circuit of the adaptor for efficiency inelectric power-transformation. In this method, a large toroidal coil, toseparate and insulate the output circuit from the commercial powersource, and, several kinds of coils for energy accumulation to functionas the switching regulator, are used.

[0006] Although the switching regulator method occupies the mainstreamof means to realize an AC adaptor of high efficiency and small size incurrent electronic technology, making a thin case body of the adaptorhas to be restricted by the coil having a toroidal core and the coils ofseveral other kinds as indispensable components for the circuit.

[0007] Generally, in the AC adaptor of the switching regulator method,thickness of the case body becomes unavoidably large for the physicalconfigurations of the used parts, the configuration of the case body hasto be box-type to minimize the volume, and inconvenience or inadequacymay be caused when the adaptor is carried with a portable appliance.

[0008] In view of the above situation, the present invention, forexample, a transformer assembled into an AC adaptor used for portableand other types of electronic appliances, is to provide a transformerhaving a small and flat coil instead of the coil with the toroidal corewhich governs the thickness of the appliance, and able to providenecessary performance with an extremely thin form.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The present invention will be described with reference to theaccompanying drawings in which:

[0010]FIG. 1 is a top view showing an embodiment of a primary-side coilof the present invention;

[0011]FIG. 2 is a top view showing an embodiment of a secondary-sidecoil of the present invention;

[0012]FIG. 3 is a top view showing an embodiment of a shielding layer ofthe present invention;

[0013]FIG. 4 is a cross-sectional side view of a transformer;

[0014]FIG. 5 is an explanatory view showing through hole terminalportions;

[0015]FIG. 6 is an explanatory view showing through hole portions forshielding of the coil;

[0016]FIG. 7 is an explanatory view showing through hole portions forshielding of the shielding layer;

[0017]FIG. 8 is a concrete circuit diagram in which the transformer ofthe present invention is used;

[0018]FIG. 9 is an explanatory view showing wave forms of respectiveportions in the circuit of FIG. 8;

[0019]FIG. 10 is another concrete circuit diagram; and

[0020]FIG. 11 is an explanatory view showing wave forms of respectiveportions in the circuit of FIG. 10.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The present invention, for example, relates to a transformerassembled into an AC adaptor as a form of a power source to obtaindirect current from a commercial power source. Although this AC adaptormay have different internal constructions according to its purposes,switching regulator method is used in most cases in which large amountof electric power is handled with a small-sized and light-weightadaptor. With this method, although the adaptor can be small-sized andlight-weight for very high efficiency in electric power transformation,a case body of the adaptor is restricted to being thin for physicaldisposition of coils with toroidal core to compose the circuit. Thepresent invention establishes an art which can provide a very thin ACadaptor, although having a slight reduction of the efficiency inelectric power transformation, by realizing a high-frequency coilfunctioning in place of the coil with toroidal core as a key component.

[0022] To describe concretely, electric power from a commercial powersource of 50 Hz or 60 Hz is preliminary transformed into high-frequencyalternate current, and then, the voltage is transformed by a super-flathigh-frequency transformer having a predetermined construction at ahigh-frequency level. In this high-frequency transformer, a primaryside, directly connected to the commercial power source, and a secondaryside, connected to an appliance, are entirely separated and insulateddynamically.

[0023] This high-frequency transformer has a super-flat coil composed ofa multilayer substrate construction for its characteristics dealing withhigh frequency. And, in the high-frequency transformer, shielding layersto shield excessive electromagnetism radiated outward is provided, andferrite material, having good high-frequency characteristics and smallmagnetism loss, is painted or vapor-depositioned on an upper and a lowersurface of the shielding layer and inner parts of through holes asshielding portion disposed on a peripheral portion and a central portionof the transformer to enhance total efficiency of electricitytransmission together with magnetism shielding ability.

[0024]FIG. 1 is a top view (construction view of each part) of asuper-low-profile high-frequency coil forms a main portion in anembodiment of the present invention. FIG. 1 shows a pattern used as aprimary-side coil 1. Three primary-side coils are used in the presentembodiment.

[0025]FIG. 2 shows a pattern used as a secondary-side coil 2. Threesecondary-side coils are used in the present embodiment.

[0026]FIG. 3 is a top view of an upper shielding layer 3 and a lowershielding layer 4 respectively disposed on the upper and the lower sideof the transformer in the present embodiment.

[0027] In the present embodiment, as shown in FIG. 4, three primary-sidecoils 1 a, 1 b, and 1 c, and three secondary-side coils 2 a, 2 b, and 2c are disposed as to be layered in turn to form a multilayerconstruction B, and the upper shielding layer (upper shielding plate) 3is disposed on an upper position and the lower shielding layer (lowershielding plate) 4 is disposed on a lower position in the multilayerconstruction to compose a high-frequency coil 7 of a eight-layersubstrate construction.

[0028]FIG. 5 shows through hole terminal portions 5 to connect (conduct)the coils of each layer (the shielding layers 3 and 4) through the wholelayers from the upper shielding layer 3 to the lower shielding layer 4,FIG. 6 shows through hole portions 6 for shielding through the wholelayers of the multilayer construction B, and FIG. 7 shows the throughhole portions 6 for shielding (patterned portion for shielding) of theupper shielding layer 3 and the lower shielding layer 4 on the uppermostlayer and the lowermost layer of the high-frequency coil 7. In FIGS. 5through 7, many independent circular patterns unconnected each other aredisposed as eddy current generated on individual circular patterns donot confluent each other.

[0029]FIG. 4 is a cross-sectional side view of the eight-layer substrateconstruction as the present embodiment composed of a first layer as theshielding layer (the upper shielding layer 3), a second layer as theprimary-side coil layer 1 a, a third layer as the secondary-side coillayer 2 a, a fourth layer as the primary-side coil layer 1 b, a fifthlayer as the secondary-side coil layer 2 b, a sixth layer as theprimary-side coil layer 1 c, a seventh layer as the secondary-side coillayer 2 c, and a eighth layer as the lowermost layer (the lowershielding layer 4). The first layer as the shielding layer (the uppershielding layer 3), the eighth layer as the shielding layer (the lowershielding layer 4), and the shielding through hole portions 6 on theperiphery and the central portion of the multilayer construction B onwhich ferrite material is disposed (painted or vapor-depositioned) areshown in black. That is to say, the ferrite material is disposed onthese through holes to make the shielding through hole portions 6, andthe parts on which the ferrite material is painted or vapor-depositionedform an EI core construction in which an E core and an I core arecombined, namely, a complete electromagnetism confining construction.

[0030] To describe further in detail, in the transformer of the presentinvention, the spiral primary-side coil 1 of thin plate composed of aprinted pattern and the spiral secondary-side coil 2 of thin platecomposed of a printed pattern are layered in turn to form the multilayerconstruction B. And, the primary-side coils 1 a, 1 b, and 1 c areconnected (electrically conducted) each other by insertion of conductingpins to the through hole terminal portions 5, the secondary-side coils 2a, 2 b, and 2 c are connected (electrically conducted) each other byinsertion of conducting pins to the through hole terminal portions 5,and the upper shielding layer 3 of thin plate and the lower shieldinglayer 4 of thin plate are respectively disposed as the uppermost layerand the lowermost layer of the multilayer construction B. Theprimary-side coils and the secondary-side coils can be connected asdescribed above with the conducting pins because the end portion of thespiral coil as the primary-side coil 1 in FIG. 1 is connected to a rightthrough hole terminal portion 5 a, and the end portion of the spiralcoil as the secondary-side coil 2 in FIG. 2 is connected to a leftthrough hole terminal portion 5 b.

[0031] To describe the shielding through hole portion 6 further, theferrite material having good high-frequency characteristics and smallmagnetic loss is disposed on the surface of the upper shielding layer 3,the surface of the lower shielding layer 4, a peripheral side portion ofthe multilayer construction B (namely, a peripheral side portion of thehigh-frequency coil 7), and inner peripheral portions (central portions)of the primary-side coils 1 and the secondary-side coils 2. Thetransformer has a construction to confine the generated magnetic fieldmore strictly to enhance total efficiency in electric power transmissionwith the ferrite material painted or vapor-depositioned on theseportions.

[0032] With the construction above, the uppermost and lowermost layers,the peripheral portion of the high-frequency coil 7, and the centralportions of the spiral coils are perfectly connected with the shieldingthrough hole portions 6 (the through holes on which the ferrite materialis disposed), each of the primary-side coils 1 and the secondary-sidecoils 2 is wrapped to shield high-frequency electric field. Therefore,the high-frequency transformer can efficiently transmit the electricpower transformed into high-frequency.

[0033]FIG. 8 is a concrete circuit diagram in which thesuper-low-profile high-frequency coil of the present invention is used.Commercial AC power is rectified through a low-velocity rectifiercircuit 10 and transformed into direct current including ripples througha smoothing circuit 11. This is shown with a wave form A of (a) in FIG.9. A high-frequency generation circuit 14 driven by a stabilizedlow-voltage circuit 13 generates regular high frequency. This is shownwith a wave form B of (b) in FIG. 9. This output is driving ahigh-frequency switching circuit 12 and given to the primary-side coil 1of the super-low-profile high-frequency coil as a high-frequency signalmodulated by the wave form A as shown with a wave form C of (c) in FIG.9. The primary-side coil 1 of the super-low-profile high-frequency coilis circuitally processed as to resonant with the switching drivehigh-frequency under the service condition.

[0034] In the secondary-side coil 2 tightly connected to theprimary-side coil 1 of the super-low-profile high-frequency coil,decreased high-frequency voltage, determined by winding ratio of theprimary and secondary coils, is generated. This is detected andrectified by a high-velocity rectifier circuit 20 and smoothed by asmoothing circuit 21 to obtain low-voltage direct current includingripples shown with a wave form D of (d) in FIG. 9. Required stabilizedDC output is obtained from the DC power through a DC-DC switchingregulator circuit composed of a DC-DC switching circuit 22, areference-voltage generation circuit 23, and an error-voltage controlcircuit 24. Several ripples caused by comparative error are included inthe stabilized output as shown with a wave form E of (e) in FIG. 9.

[0035]FIG. 10 is a concrete circuit diagram in which thesuper-low-profile high-frequency coil of the present invention is used.Although basic construction of the circuit is similar to that of FIG. 8,the control method of the DC-DC switching regulator circuit is changedas that a photo coupler composed of a photo diode 25 and a phototransistor 16 removes primary and secondary isolation, signal of theerror-voltage control circuit is lead to the switching control circuit15 on the primary side, and the high-frequency switching circuit 12itself is directly controlled to stabilize the DC output voltage on thesecondary side.

[0036] The output wave form of the error-voltage control circuit 24 isas shown with a wave form F of (h) in FIG. 11. And, the working waveform of the high-frequency switching circuit 12 in the present method,as shown with a wave form G of (i) in FIG. 11, follows the state of theprimary-side modulation voltage and the variance of the secondary-sideoutput power, and changes the high-frequency electric energy sent to theprimary-side coil 1 to obtain the required stability of thesecondary-side output. However, in the present method, as a wave form Hof (i) in FIG. 11, remaining ripples caused by control time response ofthe circuit may be worse than that of the circuit composition of FIG. 8.

[0037] According to the transformer of the present invention, realizingthe super-low-profile high-frequency coil functioning instead of thecoil with a toroidal core, an extremely thin transformer, although theefficiency of electric power transform is slightly lowered, can becomposed to provide, for example, a small adaptor.

[0038] And, generated magnetic field is strictly confined further toenhance the total efficiency of power transmission with the ferritematerial painted or vapor-depositioned on predetermined positions.

[0039] While preferred embodiments of the present invention have beendescribed in this specification, it is to be understood that theinvention is illustrative and not restrictive, because various changesare possible within the spirit and indispensable features.

What is claimed is:
 1. A transformer comprising a multilayerconstruction composed of plural spiral primary-side coils of thin plateand plural spiral secondary-side coils of thin plate layered in turn, inwhich the primary-side coils are connected each other, thesecondary-side coils are connected each other, an upper shielding layerof thin plate is disposed on an uppermost layer of the multilayerconstruction, and a lower shielding layer is disposed under a lowermostlayer of the multilayer construction.
 2. The transformer as set forth inclaim 1, wherein ferrite material is disposed on the upper shieldinglayer, the lower shielding layer, a peripheral side portion of themultilayer construction, and inner peripheral portions of theprimary-side coils and the secondary-side coils of the multilayerconstruction.